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Communication Systems International Incorporated


ISDN stands for "Integrated Services Digital Network." ISDN is a switched digital network service that allows the customer to consolidate many applications including voice, data and video, onto a single facility from the central office to the customer's premises. ISDN offers speed and quality, as well as a myriad of features and capabilities.

Key Advantages
Switching provides the power of ISDN services and enables the user to digitally connect to the public telecommunications network.

  • Ease of access: Uses existing wires via a dialed telephone number connection
  • Speed: Provides up to 1.536 Mbps connection speed.
  • Supports multiple calls: Handles up to 23 calls at the same time.
  • Cost Savings: Saves money by consolidating lines.
  • Flexibility:
    • Allocates bandwidth on single line to handle various forms of information including voice, data, compressed video, facsimile and images.
    • Circuit switchings gives you choices on where to communicate, what to send and how to send it.
  • Line Features: Offers features available due to ISDN signaling.
  • Universal connectivity: Connects easily to any other ISDN circuit.
  • Reliable network, equipment, services:
    • 99.9% services availability
    • 24 hour network monitoring

ISDN Prime Applications

  • Cost Savings via consolidation of network facilities, particularly analog PBX/DID lines.
  • Remote LAN access
  • PBX to PBX connectivity
  • Private line backup for disaster recovery
  • Videoconferencing
  • Distance learning
  • Electronic libraries
  • Telemedicine
  • Image transfer

Pure Voice ISDN Prime Application
Incoming dial calls can come from any outside telephone via POTs, Centrex, PBX, long distance or 800 calls/lines into a PBX or Key System unit (KSU). Outgoing calls from the PBX's telephone stations could be of any type including local, long distance, 800, etc. Typically this application exists because the customer migrated from existing analog PBX/DID lines to a digital trunking ISDN PRI line.

Pure Data Application
Pure data applications using PRI are encountered less frequently than pure voice but are expected to grow rapidly in popularity as remote access applications become more common. Like AT&T®'s ROAM service, this application is most commonly used as remote PC users are accessing LAN-based data applications, usually on host application servers or PCs, through a router on a LAN. Users could be sales representatives using a Lotus Notes application from home, students using remote connectivity to access homework or email, or any other common remote access application.

ISDN Prime Voice, Data, Video Hybrid Application
This type of hybrid application will be encountered more in the near future as convergence of voice, data and video becomes more prevalent in the industry.

ISDN Prime Features
The following table contains information on the most common features and capabilities of ISDN Prime.




Service Selection

(also known as Dynamic Allocation of Bandwidth)

Dynamic Allocation of Bandwidth is the capability to use a single trunk group to access a variety of services. Without this feature, users must configure a separate set of trunks for each network services that they use, such as Outbound WATS, 800 Services, etc. On a local basis, Direct Inward Dialing, Direct Outward Dialing, 800 services.

With Call-By-Call Service Selection, any B Channel can be used to support any network service. Rather than paying for dedicated access trunks with each service, the access trunks (B Channels) can be pooled and used for any type of call. The user requires fewer trunks overall to meet the calling requirements.

(PBX Trunk Consolidation)

Sometimes up to 30 or more separate DID/DOD, tie, INWATS, OUTWATS, data, etc. DSO (64 Kbps) PBX trunks can be consolidated into one PRI link with 23 channels.

Frequently, the total number of such trunks required can be reduced because of the ability to allocate the channels of a call-by-call basis, thereby allowing for growth potential.

Voice, Data, VIdeo Hybrid Applications (PBX/Hybrid networking)

Ameritech ISDN Prime is an ideal vehicle for networking PBX locations or a mixture of PBX locations and Ameritech Centrex locations, or any combination of voice, data or video.

Consolidation of applications onto one circuit is an efficient use of resources.

D Channel

Allows call setup/tear down, Caller ID and other message are performed on D channel. Information such as Caller ID, to be passed over the D channel.

Frees all 23 B channels to be used as 64 KB call paths for customer traffic. Increases call processing speed.

D Channel Multiple Primes

Non-Facility Associated Signaling (NFAS)

D Channel Multiple Primes (or NFAS) describes PRI configurations where a single D channel supports multiple primes.

Provides more bandwidth for customer application.

D Channel Back-Up (BDCH)

In PRI applications using Non-Facility Associated Signaling (NFAS), continuous operation of the shared D Channel will be critical. if the interface carrying the D Channel fails, it will be impossible to make calls. D Channel Back-Up D Channel on another PRI. The BDCH must be configured on a higher facility than the Primary DCH and must have an interface identifier (IID) of one (1). Care should be taken when arranging facilities on the CO peripherals that the Primary and BDCH are not assigned to the same switch card.

Provides backup for failed D channels when multiple ISDN Prime pipes share a single D channel in the same trunk group. D Channel Back-Up is recommended when Non-Facility ASsociated Signaling is used to control more than three Prime circuits.

Fast Set-Up

With Fast Set-up, a single exchange of signaling messages is used to set-up or tear-down a connection; derived from D channel.

This feature should help reduce the amount of time required to establish a call.

Calling Line Identification/
Caller ID

Allows the network to send the telephone number of the calling party when a call is delivered. The calling number is sent in a field in a D Channel signaling message.

Allows a customer file to automatically be sent to a service rep. Lets individual decide whether the call merits interruption or can be taken at a later time.

Computer Telephony Integration (CTI) Applications

Can accommodate hundreds of applications available ranging from enterprise-level Automatic Call Distribution to Desktop Contact Management. Most rely on "screen pops" - data brought to the user's computer screen based on the calling party's telephone number.

Utilizes Caller ID and Fast Set-up capabilities for Call Center applications.

Calling Name Display (CNAM)

The name of the calling party is sent along with the telephone number.

Provides an added level of Caller ID and allows the name of the caller to be displayed instead of just the number.

64 K Clear Channel Capability (64 CCC)

The entire 64 Kbps channel is used for data; D channel provides all control signaling.

Efficient use of bandwidth permits use of all 64 Kbps instead of just 56Kbps.

2B Channel Transfer

Allows the controlling party (A) to place a call on hold (B), add a third party (C) and then to transfer Caller B to Caller C while releasing B's channel that connected A to the central office.

Minimizes the contention on B channels when the parties are not actively using the facility.

Equal Access

Customer is able to pre select an IXC for each trunk group enabled on the ISDN Prime.

Allows the customer to consolidate all of their traffic, both local and long distance, over one high capacity traffic route.

Fiber Ring Capability

AT&T®'s Prime can be served over a fiber ring since it utilizes a digital DS1 facility as a local loop.

Provides the capabilities for switching to redundant system in the event of main system failure.


Voice Services

Access Lines

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